The head of Russia's Constitutional Court likened U.S. President Barack Obama's public comments about American "exceptionalism" to Nazi propaganda, taking Russian verbal attacks on Obama and U.S. foreign policy to a new level.

The comments by Constitutional Court chief Valery Zorkin at a St. Petersburg legal forum come at a time when tension between Moscow and Washington is at a height unseen since the end of the Cold War.

Zorkin is no stranger to controversial public statements. In 2014, he published a long essay in the government daily Rossiiskaya Gazeta that defended the institution of serfdom, which Tsar Alexander II abolished in 1861.

In his remarks on May 19, Zorkin said that the concept of American "exceptionalism" has increasingly manifested itself in U.S. foreign policy in recent years, and called this a worrying trend.

"Any objective, educated person can see in Obama's statements an almost verbatim quoting of the leading politicians and propagandists of Germany's Third Reich, including Adolf Hitler," Zorkin was quoted by the state-run RIA Novosti news agency as saying.

"At heart, what Obama is declaring is the same as what the Nazi bigwigs were saying about the exceptionalism of the Germans and Germany as they unleashed a world war," Zorkin added.

He gave no specific examples of "almost verbatim quoting."

Obama has publicly described the United States as an "exceptional" nation on numerous occasions. His domestic political opponents have frequently accused him of being insufficiently committed to the concept.

Russia has long bristled at NATO's eastward expansion and what it considers U.S. attempts to pull former Soviet bloc nations away from Moscow's influence.

Relations between the two countries have plummeted further since Russia’s military seizure of Ukraine's Crimean Peninsula in March 2014 and subsequent backing of armed separatists battling Kyiv's forces in the east of the country.

The Obama administration has sought to isolate Russia in response to Moscow's actions in Ukraine and punished senior Russian officials, Kremlin insiders, and state-owned companies with sanctions.

Zorkin has been chairman of the Constitutional Court since 2003 and also held the post from 1991-93.

In his 2014 essay, he described serfdom as the "staple" that held Russian society together and that its abolition exacerbated "social tensions."